A bump is an important component in a flip-chip package structure for connecting a substrate and chip. The flip-chip package structure often applies the bump as an agent to mechanically or electrically connect the substrate and the chip. The bump is crucial for the connection between the substrate and the chip, as the reliability of the bump affects the operation of the whole flip-chip package structure. The purpose of packaging is to protect the chip during various processes and attach a packaged chip onto a printed circuit board. However, any damage during packaging to the chip is not acceptable.
Reflow process is the most common method of attaching surface mount components to a circuit board and/or a metal pad. For better reliability and attachment to the metal pad, the bump is processed through the reflow process. In the reflow process, the entire assembly of the circuit board and bump is under a thermal treatment, such as by annealing. The thermal treatment may be accomplished by passing the assembly through a reflow oven or under an infrared lamp. Accordingly, it is essential to improve the reliability of the bump in the packaging process.